A crimp or press-style fitting is typically a tubular sleeve containing seals. The fitting is compressed in radial directions to engage the ends of pipes. The fitting forms a leak resistant joint between the pipe ends. The joint has considerable mechanical strength and is self-supporting. A crimping tool and crimping assembly are used to crimp the fitting. The crimping assembly can include jaws activated by the crimping tool for directly crimping the fitting. Alternatively, for larger fittings, the crimping assembly can be an actuator assembly having arms that actuate a crimp ring to crimp the fitting.
Referring to FIG. 1, components of a typical crimping tool 10, actuator assembly 18, and crimp ring 50 in accordance with the prior art are illustrated. The crimping tool 10 and actuator assembly 18 are shown partially unassembled to reveal relevant details. The crimping tool 10 includes a cylinder 12, a hydraulic piston 14, and an engagement member 16, such as a carriage having rollers 17. The actuator assembly 18 couples to the crimp tool 10 by methods known in the art. The actuator assembly 18 includes first and second actuator arms 20a and 20b, first and second side plates 40 and one not shown, and pivot pins 44.
Each actuator arm 20a and 20b includes a cam end 22 and a crimp end 24. The cam end 22 includes a surface 23 for contacting one of the rollers 17 of the engagement member 16 attached to the end of the hydraulic piston 14. The surfaces 23 of the prior art do not control the input force applied thereon by the rollers 17 versus displacement of the piston 14 when used with various fittings. Typically, the surfaces 23 of the prior art include a portion defined by a radius and include a portion defined by a line. In the present example, the crimp ends 24 of the arms 20a and 20b couple to the crimp ring 50 to crimp larger fittings.
The crimp ring 50 has a plurality of ring portions. In the present example, the crimp ring 50 has two portions 52a and 52b with each having an indentation 54 for receiving a crimp end 24 of the arms 20a and 20b. The portions 52a and 52b are pivotably connected together by a pin 56. The crimp ends 24 of the arms 20a and 20b couple respectively to the portions 52a and 52b. 
In the prior art, the actuator arms 20a and 20b each define pockets 34, as best shown by the cross-section of arm 20b. The pocket 34 has two sidewalls 36 with one not shown in the cross-section of arm 20b. The two sidewalls 36 each define an indentation 36. The actuator assembly 18 includes a torsion spring 30 and a pin 32. The pin 32 disposes in the torsion spring 30. The spring 30 and pin 32 are positioned in the pockets 34 between the arms 20a and 20b. The pin 32 fits into the indentations 38 in the sidewalls 36 to hold and stabilize the spring 30. The spring 30 biases the crimp ends 24 together, which facilitates handling of the assembly 18 and crimp ring 50 when positioning on a fitting.
In operation, a hydraulic pump (not shown) builds up hydraulic pressure in the cylinder 12 to move the piston 14 and press the rollers 17 of the engagement member 16 against the arms 20a and 20b. The rollers 17 engage the surfaces 23 of the arms 20a and 20b, causing the arms 20a and 20b to rotate. Depending on the intake angle of the rollers 17 on the surfaces 23, a crimping force up to about 100 kN may be produced when measured at the crimp coupling centerline. Typically, the crimping time may be about 4 seconds, and the hydraulic output may be about 32 kN from the piston 14 of the crimping tool 10 to produce the input force to the crimping assembly 18.
When the arms 20a and 20b are actuated by displacement of the engagement member 16 associated with the hydraulic piston 14, the crimp ends 24 move together to actuate the crimp ring 50. The developed crimping force closes the portions 52a and 52b about the fitting. In some embodiments, the crimp ring 50 may pivot on the crimp ends 24 to enable an operator to crimp the fitting in locations of obstructed or limited accessibility.
The life and failure mode of crimping assemblies of the prior art, such as discussed above, may be unacceptable. The actuator arms undergo intense forces when crimping and can fail, which is undesirable. In the prior art, crimping assemblies have included straps attached to the arms to retain them on the assembly if they do fail.
In addition, crimping assemblies of the prior art may not always give an ideal or near ideal crimp on the fitting. In other words, the prior art crimping assemblies may not uniformly apply a crimping force to the fitting over the displacement of the piston. Furthermore, the force versus displacement profiles of the prior art crimping assemblies may not be consistent when used with fittings of various sizes, materials, or tolerances and especially when used with fittings having larger diameters up to 4-in.
Referring to FIGS. 2A–F, graphs of force profiles 60a–f are provided from test results using a prior art actuator assembly to actuate typical crimp rings to crimp fittings of various sizes. In FIGS. 2A–F, the input force (kN) as applied to the piston (14) is plotted against the piston displacement (in.) of the hydraulic piston engaging the actuator assembly. Each force profile 60a–f includes plots of three crimp operations.
Force profiles 60a–f illustrate test results using the prior art actuator assembly actuating typical, prior art crimp rings to crimp a 2.5-in. fitting on type K copper tubing, a 2.5-in. fitting on type M copper tubing, a 3-in. fitting on type K copper tubing, a 3-in. fitting on type M copper tubing, a 4-in. fitting on type K copper tubing, and a 4-in. fitting on type M copper tubing, respectively. In all cases, the material and geometry of the copper tubing are governed by the standard specification, ASTM B88, for seamless copper water tubing. For the force profiles 60a–f, the piston displacement of 0-inch corresponds to the point where the rollers 16 just make contact with the surfaces 23 of the arms 20a and 20b while the crimp ring 50 contacts an undeformed fitting. For clearance and for opening the actuator, it is understood that additional displacement of the piston of 2 to 3-mm typically exists before the rollers 16 make contact with the surfaces 23.
Each of the force profiles 60a–f includes an initial portion 62, a sustained portion 64, and a ramp portion 66. Some of the force profiles 60a–f require a significant amount of stroke to reach the sustained portion 64. For example, the force profile 60a in FIG. 2A requires roughly 0.6-in. of displacement before reaching 20 kN. The force profile 60b in FIG. 2B requires roughly 0.7-in. of displacement before reaching 20 kN. Some of the force profiles 60a–f have peaks where the force spikes generally higher than is ideally desirable when crimping fittings of various diameters. For example, the force profile 60d in FIG. 2D includes a peak 65 approaching nearly 30 kN at the displacement of approximately 0.9-in. Some of the force profiles 60a–f have sustained portions 64 with a higher force in general than is ideally desirable when crimping fittings of various diameters. For example, in the force profile 60c in FIG. 2C, the sustained portion 64 attains a level between 26 and 28 kN.
In the force profiles 60a–f, the total stroke (i.e., displacement of the hydraulic piston) extends for a longer displacement than is ideally desirable when crimping fittings of various diameters. The prior art actuator assembly and crimp rings require an excessive amount of stroke on the order of over 1.4-in. to crimp the larger fittings of 2.5, 3, and 4-in. The stroke length of over 1.4-in. is excessive when compared to the amount of stroke used by smaller sized assemblies, such as a 0.5-in. stroke for a ½-in. jaw assembly and a 1.2-in. stroke for a 2-in. jaw assembly.
The stroke length of over 1.4-in. is also excessive when compared to the amount of stroke available in a typical crimping tool. For example, the total available stroke of the typical crimping tool is approximately 40-mm or 1.57-in. with approximately 36-mm or 1.42-in. of that stroke being desirable for use in normal designs to accommodate manufacturing tolerances and to allow for clearance between the rollers and the actuator arms. Requiring over 1.4-in. of stroke length, the prior art crimping assembly lies close to the usable stroke limit.
Additionally, the prior art actuator assembly and crimp ring used to crimp the 3-in. fitting exhibited a tendency towards an excessively high peak 65 before reaching the final force of 32 kN. As shown in FIG. 2D, the peak is nearly 30 kN. If the premature peak triggers the pressure relief setting of 32 kN, this premature peaking could potentially cause the crimping tool to shut down before a completed crimp is formed with the actuator assembly and crimp ring. It is understood that the pressure relief setting of 32 kN can vary within a range, depending on the specific tool or type of tool being used and depending on a number of variables, such as voltage levels, tolerances, and temperature effects, among other variables.
The present invention is directed to overcoming or at least reducing one or more of the problems set forth above.